Electrode catheters are used to apply RF current (or other forms of electrical energy) within the heart to destroy (ablate) accessory atrioventricular pathways which provide an abnormal electrical connection between the atria and ventricles and produce arrhythmias (heart rhythm disorders). Ablation of the accessory pathway eliminates the arrhythmias.
In such an ablation procedure, the electrode tip of the catheter is brought into and maintained in contact with the endocardium (inner lining of the heart) close to the site of the accessory electrical pathway. When RF current is delivered through the catheter, a small lesion is created by the production of heat due to current passing through the heart tissue, ablating the accessory pathway and a small region of adjacent heart tissue.
In this procedure, the electrode must remain in firm, steady contact with the endocardium. Present catheter electrodes used for electrophysiologic studies of the heart and for ablation procedures in the heart have a generally cylindrical shape with a smooth, rounded distal tip 1, as shown in FIG. 1, or have a smooth, oval-shaped tip 1a, as shown in FIG. 2. Such rounded tip catheters are designed to minimize trauma to the heart. The oval-shaped electrode of FIG. 2 is designed primarily for ablation procedures using high voltage, short duration, direct current shocks, and this shape eliminates the proximate edge of the electrode which otherwise would have a high current density, yet not be in contact with the endocardium. However, both electrode shapes tend to slide along the heart surface. This tendency makes it difficult, in some locations of the heart, such as the mitral annulus and tricuspid annulus, to maintain steady contact between the electrode and the endocardium to adequately deliver the required RF current.